Device for self-assembling semiconductor light-emitting diodes

ABSTRACT

Discussed is a device for self-assembling semiconductor light-emitting diodes, in which the device includes an assembly chamber having a space for accommodating a fluid; a magnetic field forming part having at least one magnet for applying a magnetic force to the semiconductor light-emitting diodes dispersed in the fluid and a moving part for changing positions of the at least one magnet so that the semiconductor light-emitting diodes move in the fluid; a substrate chuck having a substrate support part configured to support a substrate, and a vertical moving part for lowering the substrate so that one surface of the substrate is in contact with the fluid in a state in which the substrate is supported by the substrate support part; and a controller for controlling a movement of the magnetic field forming part and the substrate chuck, wherein the controller controls a depth at which the substrate is submerged in the fluid based on a degree of warping of the substrate.

CROSS-REFERENCE TO RELATED APPLICATION

Pursuant to 35 U.S.C. § 119(a), this application claims the benefit ofearlier filing date and right of priority to Korean Patent ApplicationNos. 10-2019-0115574, filed on Sep. 19, 2019 and 10-2019-0119008, filedon Sep. 26, 2019, the contents of all of these applications areincorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to a method for manufacturing a displaydevice, and more particularly, to a device for self-assemblingmicroLEDs.

2. Description of the Related Art

In recent years, in the field of display technology, liquid-crystaldisplays (LCD), organic light-emitting diode (OLED) displays, microLEDdisplays, etc. have been competing to realize large-area displays.

Meanwhile, semiconductor light-emitting diodes (microLEDs (μLED)) with adiameter or cross-sectional area less than 100 microns, when used indisplays, can offer very high efficiency because the displays do notneed a polarizer to absorb light. However, large-scale displays requireseveral millions of semiconductor light-emitting diodes, which makes itdifficult to transfer the devices compared to other technologies.

Some of the technologies currently in development for the transferprocess include pick and place, laser lift-off (LLO), and self-assembly.Among these technologies, the self-assembly approach is a method thatallows semiconductor light-emitting diodes to find their positions ontheir own in a fluid, which is most advantageous in realizinglarge-screen display devices.

Recently, U.S. Pat. No. 9,825,202 disclosed a microLED structuresuitable for self-assembly, but there is not enough research beingcarried out on technologies for manufacturing displays by theself-assembly of microLEDs. In view of this, the present disclosureproposes a new manufacturing device for self-assembling microLEDs.

SUMMARY OF THE INVENTION

One aspect of the present disclosure is to provide a new manufacturingprocess that provides high reliability in large-screen displays usingmicro-size semiconductor light-emitting diodes.

Another aspect of the present disclosure is to provide a device forcorrecting a warpage phenomenon of a substrate caused by gravity when asemiconductor light-emitting diode is self-assembled on a temporarysubstrate or a wiring substrate.

In addition, still another aspect of the present disclosure is toincrease a self-assembly yield by removing bubbles generated when thesubstrate is in contact with a fluid.

Further, still another aspect of the present disclosure is to preventthe previously assembled semiconductor light-emitting diode from beingseparated from the substrate when the substrate is separated from thefluid after self-assembly is completed.

In order to achieve the above-described aspect, the present disclosureprovides a device for self-assembling semiconductor light-emittingdiodes, which includes: an assembly chamber having a space foraccommodating a fluid, a magnetic field forming part having a pluralityof magnets for applying magnetic force to the semiconductorlight-emitting diodes dispersed in the fluid and a horizontal movingpart for changing positions of the magnets so that the semiconductorlight-emitting diodes move in the fluid, a substrate chuck having asubstrate support part configured to support a substrate having anassembly electrode, a vertical moving part for lowering the substrate sothat one surface of the substrate is in contact with the fluid in astate in which the substrate is supported, an electrode connection partfor applying power to the assembly electrode to generate an electricfield so that the semiconductor light-emitting diodes are placed atpredetermined positions of the substrate in a process of moving by aposition change of the magnets, and a controller for controllingmovement of the magnetic field forming part and the substrate chuck,wherein the controller controls a depth at which the substrate issubmerged in the fluid based on a degree of warping of the substrate.

In one embodiment, a displacement sensor for sensing a degree of warpingof the substrate can be further included, wherein the controller cancontrol a depth at which the substrate is submerged in the fluid basedon a sensing result of the displacement sensor.

In one embodiment, the controller lowers the substrate such that anassembly surface of the substrate is in contact with the fluid, and thencan further lower the substrate in a state in which the assembly surfaceof the substrate is in contact with the fluid.

In one embodiment, the substrate chuck can include a rotating part forrotating the substrate support part, and the controller can drive thevertical moving part and the rotating part such that the assemblysurface of the substrate is obliquely in contact with the fluid whenlowering the substrate such that the assembly surface of the substrateis in contact with the fluid.

In one embodiment, the controller can control the vertical moving partto lower the substrate until one end of the assembly surface is incontact with the fluid in a state in which the assembly surface of thesubstrate is disposed obliquely to the surface of the fluid, and cancontrol the rotating part such that the assembly surface is sequentiallyin contact with the fluid along one direction after one end of theassembly surface is in contact with the fluid.

In one embodiment, after an entire assembly surface is in contact withthe fluid, the controller can control the vertical moving part to lowerthe substrate.

In one embodiment, after the semiconductor light-emitting diodes areplaced at a predetermined position, the controller can further raise thesubstrate such that the assembly surface of the substrate is separatedfrom the fluid after raising the substrate up to a predetermined height.

In one embodiment, after raising the substrate up to a predeterminedheight, the controller can drive the vertical moving part and therotating part such that the assembly surface of the substrate isobliquely separated from the fluid.

In one embodiment, after raising the substrate to a predeterminedheight, the controller can control the rotating part such that theassembly surface is sequentially separated from the fluid along onedirection.

In one embodiment, in controlling the rotating part such that theassembly surface is sequentially separated from the fluid along onedirection, the controller can control such that a rotation speed of therotating part is changed depending on a time.

In another embodiment, provided is a device for self-assemblingsemiconductor light-emitting diodes to a substrate in which the deviceincludes an assembly chamber having a space for accommodating a fluid;at least one magnet for applying a magnetic force to the semiconductorlight-emitting diodes dispersed in the fluid; a substrate supportconfigured to support the substrate having an assembly electrode; avertical mover for lowering the substrate support so that one surface ofthe substrate is in contact with the fluid in a state in which thesubstrate is supported by the substrate support; and a controller forcontrolling a movement of the at least one magnet and the substratesupport, wherein the controller controls a depth at which the substrateis submerged in the fluid.

With the above configuration according to the present disclosure, largenumbers of semiconductor light-emitting diodes can be assembled at atime on a display device where individual pixels are made up ofmicroLEDs.

As such, according to the present disclosure, large numbers ofsemiconductor light-emitting diodes can be pixelated on a small-sizedwafer and then transferred onto a large-area substrate. This enables themanufacture of a large-area display device at a low cost.

Moreover, according to the present disclosure, a low-cost,high-efficiency, and quick transfer of semiconductor light-emittingdiodes can be done, regardless of the sizes or numbers of parts and thetransfer area, by transferring them in the right positions in a solutionby using a magnetic field and an electric field.

Furthermore, the assembling of semiconductor light-emitting diodes by anelectric field allows for selective assembling through selectiveelectrical application without any additional equipment or processes.Also, since an assembly substrate is placed on top of a chamber, thesubstrate can be easily loaded or unloaded, and non-specific binding ofsemiconductor light-emitting diodes can be prevented.

In addition, according to the present disclosure, it is not necessary todispose separate structures at the upper and lower sides of thesubstrate, and a warpage phenomenon of the substrate can be corrected.Accordingly, the present disclosure enables to achieve a highself-assembly yield even when an area of the assembly substrateincreases.

Further, according to the present disclosure, it is possible to minimizebubbles generated between the substrate and the fluid when the substrateis in contact with the fluid, and thus a self-assembly yield can beincreased.

Furthermore, according to the present disclosure, it is possible toprevent the previously assembled semiconductor light-emitting diode frombeing separated from the substrate in a process of separating thesubstrate from the fluid after self-assembly is completed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram showing one embodiment of a displaydevice using semiconductor light-emitting diodes according to thepresent disclosure.

FIG. 2 is a partial enlarged view of the portion A in the display deviceof FIG. 1.

FIG. 3 is an enlarged view of the semiconductor light-emitting diodes ofFIG. 2.

FIG. 4 is an enlarged view showing another embodiment of thesemiconductor light-emitting diodes of FIG. 2.

FIGS. 5A to 5E are conceptual diagrams for explaining a new process formanufacturing the above-described semiconductor light-emitting diodes.

FIG. 6 is a conceptual diagram showing an example of a device forself-assembling semiconductor light-emitting diodes according to thepresent disclosure.

FIG. 7 is a block diagram of the self-assembly device of FIG. 6.

FIGS. 8A to 8E are conceptual diagrams showing a process forself-assembling semiconductor light-emitting diodes using theself-assembly device of FIG. 6.

FIG. 9 is a conceptual diagram for explaining the semiconductorlight-emitting diodes of FIGS. 8A to 8E.

FIG. 10 is a flowchart showing a method for self-assembly according tothe present disclosure.

FIG. 11 is a conceptual diagram showing a first state of a substratechuck.

FIG. 12 is a conceptual diagram showing a second state of a substratechuck.

FIG. 13 is a plan view of a first frame provided at a substrate chuck.

FIG. 14 is a conceptual diagram showing a state in which an assemblysubstrate is loaded at a substrate chuck.

FIG. 15 is a perspective view of a magnetic field forming part accordingto one embodiment of the present disclosure.

FIG. 16 is one side view of a magnetic field forming part according toone embodiment of the present disclosure.

FIG. 17 is a lower side view of a magnetic field forming part accordingto one embodiment of the present disclosure.

FIG. 18 is a conceptual diagram showing a trajectory of magnets providedat the magnetic field forming part according to the present disclosure.

FIG. 19 is a conceptual diagram showing a state in which a semiconductorlight-emitting diode is supplied.

FIG. 20 is a plan view of an assembly chamber according to oneembodiment of the present disclosure.

FIG. 21 is a cross-sectional view taken along line A-A′ of FIG. 20.

FIGS. 22 and 23 are conceptual views showing movement of a gate providedat an assembly chamber according to one embodiment of the presentdisclosure.

FIG. 24 is a conceptual diagram showing a warpage phenomenon of asubstrate generated during self-assembly.

FIG. 25 is a conceptual diagram showing a method for correcting awarpage phenomenon of a substrate.

FIG. 26 is a flowchart showing a method for correcting a warpagephenomenon of a substrate.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Description will now be given in detail according to example embodimentsdisclosed herein, with reference to the accompanying drawings. For thesake of brief description with reference to the drawings, the same orequivalent components can be provided with the same or similar referencenumbers, and description thereof will not be repeated. In general, asuffix such as “module” and “unit” can be used to refer to elements orcomponents. Use of such a suffix herein is merely intended to facilitatedescription of the specification, and the suffix itself is not intendedto give any special meaning or function. In the present disclosure, thatwhich is well-known to one of ordinary skill in the relevant art hasgenerally been omitted for the sake of brevity. The accompanyingdrawings are used to help easily understand various technical featuresand it should be understood that the embodiments presented herein arenot limited by the accompanying drawings.

Also, it will be understood that when an element, such as a layer, areaor substrate is referred to as being “disposed on” another element, theelement can be disposed directly on the another element or there are nointervening elements present.

Mobile terminals described herein can include cellular phones, smartphones, laptop computers, digital broadcasting terminals, personaldigital assistants (PDAs), portable multimedia players (PMPs),navigators, slate PCs, tablet PC, ultra books, digital TVs, digitalsignage, head-mounted displays (HMDs), desk top computers and the like.However, it can be easily understood by those skilled in the art thatthe configuration according to the example embodiments of thisspecification can also be applied to any device capable of displayinginformation even though such device is a new type of product to bedeveloped.

FIG. 1 is a conceptual diagram showing one embodiment of a displaydevice using semiconductor light-emitting diodes according to thepresent disclosure. FIG. 2 is a partial enlarged view of the portion Ain the display device of FIG. 1. FIG. 3 is an enlarged view of thesemiconductor light-emitting diodes of FIG. 2. FIG. 4 is an enlargedview showing another embodiment of the semiconductor light-emittingdiodes of FIG. 2.

According to the illustration, information processed by a controller ofa display device 100 can be outputted by a display module 140. A closedloop-shaped case 101 that runs around the edge of the display module canform the bezel of the display device.

The display module 140 comes with a panel 141 that displays an image,and the panel 141 can come with micro-sized semiconductor light-emittingdiodes 150 and a wiring substrate 110 where the semiconductorlight-emitting diodes 150 are mounted.

The wiring substrate 110 can be formed with wiring lines, which can beconnected to n-type electrodes 152 and p-type electrodes 156 of thesemiconductor light-emitting diodes 150. As such, the semiconductorlight-emitting diodes 150 can be provided on the wiring substrate 110 asindividual pixels that emit light on their own.

The image displayed on the panel 141 is visual information, which isrendered by controlling the light emission of unit pixels (sub-pixels)arranged in a matrix independently through the wiring lines.

The present disclosure takes microLEDs (light-emitting diodes) as anexample of the semiconductor light-emitting diodes 150 which convertcurrent into light. The microLEDs can be light-emitting diodes that aresmall in size—less than 100 microns. The semiconductor light-emittingdiodes 150 have light-emitting regions of red, green, and blue, and unitpixels can produce light through combinations of these colors. That is,the unit pixels are the smallest units for producing one color. Eachunit pixels can contain at least three microLEDs.

More specifically, referring to FIG. 3, the semiconductor light-emittingdiodes 150 can have a vertical structure.

For example, the semiconductor light-emitting diodes 150 can beimplemented as high-power light-emitting diodes that are composed mostlyof gallium nitride (GaN), with some indium (In) and/or aluminum (Al)added to it, and emit light of various colors.

Such a vertical semiconductor light-emitting diode comprises a p-typeelectrode 156, a p-type semiconductor layer 155 formed on the p-typeelectrode 156, an active layer 154 formed on the p-type semiconductorlayer 155, an n-type semiconductor layer 153 formed on the active layer154, and an n-type electrode 152 formed on the n-type semiconductorlayer 153. In this case, the p-type electrode 156 at the bottom can beelectrically connected to a p electrode of the wiring substrate, and then-type electrode 152 at the top can be electrically connected to an nelectrode above the semiconductor light-emitting diode. One of thebiggest advantages of the vertical semiconductor light-emitting diode150 is that the chip size can be reduced by vertically aligningelectrodes.

In another example, referring to FIG. 4, the semiconductorlight-emitting diodes can be flip chip-type light-emitting diodes.

As an example of such a flip chip-type light-emitting diode, thesemiconductor light-emitting diode 150′ comprises a p-type electrode156′, a p-type semiconductor layer 155′ formed on the p-type electrode156′, an active layer 154′ formed on the p-type semiconductor layer155′, an n-type semiconductor layer 153′ formed on the active layer154′, and an n-type electrode 152′ vertically separated from the p-typeelectrode 156′, on the n-type semiconductor layer 153′. In this case,both the p-type electrode 156′ and the n-type electrode 152′ can beelectrically connected to a p electrode and n electrode of the wiringsubstrate, below the semiconductor light-emitting diode.

The vertical semiconductor light-emitting diode and a horizontallight-emitting diode each can be used as a green semiconductorlight-emitting diode, blue semiconductor light-emitting diode, or redsemiconductor light-emitting diode. The green semiconductorlight-emitting diode and the blue semiconductor light-emitting diode canbe implemented as high-power light-emitting diodes that are composedmostly of gallium nitride (GaN), with some indium (In) and/or aluminum(Al) added to it, and emit green and blue light, respectively. As anexample of such high-power light-emitting diodes, the semiconductorlight-emitting diodes can be composed of gallium nitride thin filmswhich are formed of various layers of n-Gan, p-GaN, AlGaN, InGaN, etc.More specifically, the p-type semiconductor layer can be P-type GaN, andthe n-type semiconductor layer can be N-type GaN.

Moreover, the p-type semiconductor layer can be P-type GaN doped with Mgon the p electrode, and the n-type semiconductor layer can be N-type GaNdoped with Si on the n electrode. In this case, the above-describedsemiconductor light-emitting diodes can come without the active layer.

Meanwhile, referring to FIGS. 1 to 4, because of the very small size ofthe light-emitting diodes, self-emissive, high-definition unit pixelscan be arranged on the display panel, and therefore the display devicecan deliver high picture quality.

In the above-described display device using semiconductor light-emittingdiodes according to the present disclosure, semiconductor light-emittingdiodes are grown on a wafer, formed through mesa and isolation, and usedas individual pixels. In this case, the micro-sized semiconductorlight-emitting diodes 150 should be transferred onto a wafer, at presetpositions on a substrate of the display panel. One of the transfertechnologies available is pick and place, but it has a low success rateand requires a lot of time. In another example, a number of diodes canbe transferred at a time by using a stamp or roll, which, however, isnot suitable for large-screen displays because of limited yields. Thepresent disclosure suggests a new method and device for manufacturing adisplay device that can improve on these problems.

To this end, the new method for manufacturing a display device will bedescribed first below. FIGS. 5A to 5E are conceptual diagrams forexplaining a new process for manufacturing the above-describedsemiconductor light-emitting diodes.

In this specification, a display device using passive matrix (PM)semiconductor light-emitting diodes will be illustrated. It should benoted that the illustration given below also applies to active matrix(AM) semiconductor light-emitting diodes or other electrical devices.Also, although the illustration will be given of how horizontalsemiconductor light-emitting diodes are self-assembled, it also canapply to self-assembling of vertical semiconductor light-emitting diodesand other electrical devices.

First of all, according to the manufacturing method, a first conductivesemiconductor layer 153, an active layer 154, and a second conductivesemiconductor layer 155 are grown on a growth substrate 159 (FIG. 5A).

Once the first conductive semiconductor layer 153 is grown, then theactive layer 154 is grown on the first conductive semiconductor layer153, and then the second conductive semiconductor layer 155 is grown onthe active layer 154. By sequentially growing the first conductivesemiconductor layer 153, active layer 154, and second conductivesemiconductor layer 155, the first conductive semiconductor layer 153,active layer 154, and second conductive semiconductor layer 155 form astack structure as shown in FIG. 5A.

In this case, the first conductive semiconductor layer 153 can be ap-type semiconductor layer, and the second conductive semiconductorlayer 155 can be an n-type semiconductor layer. However, the presentdisclosure is not necessarily limited to this, and the first conductivetype can be n-type and the second conductive type can be p-type.

Moreover, although this example embodiment is illustrated by assumingthe presence of the active layer, the active layer can be omitted ifnecessary or desired, as stated above. In an example, the p-typesemiconductor layer can be P-type GaN doped with Mg, and the n-typesemiconductor layer can be N-type GaN doped with Si on the n electrode.

The growth substrate 159 (e.g., a wafer) can be formed of, but notlimited to, light-transmissive material—for example, at least one amongsapphire (Al₂O₃), GaN, ZnO, and AlO. Also, the growth substrate 159 canbe made from a material suitable for growing semiconductor materials orcarrier wafer. The growth substrate 159 can be formed of high thermalconducting material, and can be a conductive substrate or insulatingsubstrate—for example, at least one among SiC, Si, GaAs, GaP, InP, andGa₂O₃ substrates which have higher thermal conductivity than sapphire(Al₂O₃) substrates.

Next, a plurality of semiconductor light-emitting diodes are formed byremoving at least part of the first conductive semiconductor layer 153,active layer 154, and second conductive semiconductor layer 155 (seeFIG. 5B).

More specifically, isolation is performed so that the light-emittingdiodes form a light-emitting diode array. That is, a plurality ofsemiconductor light-emitting diodes are formed by vertically etching thefirst conductive semiconductor layer 153, active layer 154, and secondconductive semiconductor layer 155, for example.

In the case of horizontal semiconductor light-emitting diodes, a mesaprocess can be performed which exposes the first conductivesemiconductor layer 153 to the outside by vertically removing part ofthe active layer 154 and second conductive layer 155, and then isolationcan be performed which forms an array of semiconductor light-emittingdiodes by etching the first conductive semiconductor layer 153.

Next, a second conductive electrode 156 (or p-type electrode) is formedon one surface of the second conductive semiconductor layer 155 (seeFIG. 5C). The second conductive electrode 156 can be formed by adeposition method such as sputtering, but the present disclosure is notnecessarily limited to this. In a case where the first conductivesemiconductor layer and the second conductive semiconductor layer are ann-type semiconductor layer and a p-type semiconductor layer,respectively, the second conductive electrode 156 can serve as an n-typeelectrode.

Next, the growth substrate 159 is removed, thus leaving a plurality ofsemiconductor light-emitting diodes. For example, the growth substrate159 can be removed using laser lift-off (LLO) or chemical lift-off (CLO)(see FIG. 5D).

Afterwards, the step of mounting the semiconductor light-emitting didoes150 on a substrate in a chamber filled with a fluid is performed (seeFIG. 5E).

For example, the semiconductor light-emitting diodes 150 and thesubstrate are put into the chamber filled with a fluid, and thesemiconductor light-emitting diodes are self-assembled onto thesubstrate 161 using fluidity, gravity, surface tension, etc. In thiscase, the substrate can be an assembly substrate 161.

In another example, a wiring substrate, instead of the assemblysubstrate 161, can be put into an assembly chamber, and thesemiconductor light-emitting diodes 150 can be mounted directly onto thewiring substrate. In this case, the substrate can be a wiring substrate.For convenience of explanation, the present disclosure is illustratedwith an example in which the semiconductor light-emitting diodes 150 aremounted onto the assembly substrate 161.

To facilitate the mounting of the semiconductor light-emitting diodes150 onto the assembly substrate 161, cells into which the semiconductorlight-emitting diodes 150 are fitted can be provided on the assemblysubstrate 161. Specifically, cells where the semiconductorlight-emitting diodes 150 are mounted are formed on the assemblysubstrate 161, at positions where the semiconductor light-emittingdiodes 150 are aligned with wiring electrodes. The semiconductorlight-emitting diodes 150 are assembled to the cells as they move withinthe fluid.

After arraying the semiconductor light-emitting didoes on the assemblysubstrate 161, the semiconductor light-emitting diodes can betransferred to the wiring substrate from the assembly substrate 161,thereby enabling a large-area transfer across a large area. Thus, theassembly substrate 161 can be referred to as a temporary substrate.

Meanwhile, the above-described self-assembly method requires a highertransfer yield so that it can be applied to the manufacture oflarge-screen displays. The present disclosure proposes a method anddevice that minimizes the effects of gravity or friction and avoidsnon-specific binding, in order to increase the transfer yield.

In this case, in the display device according to the present disclosure,a magnetic material is placed on the semiconductor light-emitting diodesso that the semiconductor light-emitting diodes are moved by magneticforce, and the semiconductor light-emitting diodes are mounted at presetpositions by an electric field while in the process of being moved. Thistransfer method and device will be described in more details below withreference to the accompanying drawings.

FIG. 6 is a conceptual diagram showing an example of a device forself-assembling semiconductor light-emitting diodes according to thepresent disclosure. FIG. 7 is a block diagram of the self-assemblydevice of FIG. 6. FIGS. 8A to 8E are conceptual diagrams showing aprocess for self-assembling semiconductor light-emitting diodes usingthe self-assembly device of FIG. 6. FIG. 9 is a conceptual diagram forexplaining the semiconductor light-emitting diodes of FIGS. 8A to 8E.

Referring to FIGS. 6 and 7, the self-assembly device 160 of the presentdisclosure can comprise an assembly chamber 162, magnets 163, and aposition controller 164.

The assembly chamber 162 is equipped with space for a plurality ofsemiconductor light-emitting diodes. The space can be filled with afluid, and the fluid can be an assembly solution, which includes wateror the like. Thus, the assembly chamber 162 can be a water tank andconfigured as open-type. However, the present disclosure is not limitedto this, and the assembly chamber 162 can be a closed-type chamber thatcomes with a closed space.

A substrate 161 can be placed in the assembly chamber 162 so that anassembly surface where the semiconductor light-emitting diodes 150 areassembled facing downwards. For example, the substrate 161 is fed to anassembly site by a feed unit, and the feed unit can come with a stage165 where the substrate is mounted. The position of the stage 165 can beadjusted by the controller, whereby the substrate 161 can be fed to theassembly site.

In this instance, the assembly surface of the substrate 161 at theassembly site faces the bottom of the assembly chamber 162. As shown inthe drawings, the assembly surface of the substrate 161 is placed insuch a way as to be soaked with the fluid in the assembly chamber 162.Thus, the semiconductor light-emitting diodes 150 in the fluid are movedto the assembly surface.

The substrate 161 is an assembly substrate where an electric field canbe formed, and can comprise a base portion 161 a, a dielectric layer 161b, and a plurality of electrodes 161 c.

The base portion 161 a is made of insulating material, and theelectrodes 161 c can be thin-film or thick-film bi-planar electrodesthat are patterned on one surface of the base portion 161 a. Theelectrodes 161 c can be formed of a stack of Ti/Cu/Ti, Ag paste, ITO,etc.

The dielectric layer 161 b can be made of inorganic material such asSiO₂, SiNx, SiON, Al₂O₃, TiO₂, HfO₂, etc. Alternatively, the dielectriclayer 161 b can be an organic insulator and composed of a single layeror multi-layers. The thickness of the dielectric layer 161 b can rangefrom several tens of nm to several μm.

Further, the substrate 161 according to the present disclosure comprisesa plurality of cells 161 d that are separated by partition walls 161 e.The cells 161 d can be sequentially arranged in one direction and madeof polymer material. Also, the partition walls 161 e forming the cells161 d can be shared with neighboring cells 161 d. The partition walls161 e can protrude from the base portion 161 a, and the cells 161 d canbe sequentially arranged in one direction along the partition walls 161e. More specifically, the cells 161 d can be sequentially arranged incolumn and row directions and have a matrix structure.

As shown in the drawings, the cells 161 d can have recesses foraccommodating the semiconductor light-emitting diodes 150, and therecesses can be spaces defined by the partition walls 161 e. Therecesses can have a shape identical or similar to the shape of thesemiconductor light-emitting diodes. For example, if the semiconductorlight-emitting diodes are rectangular, the recesses can be rectangulartoo. Moreover, the recesses formed in the cells can be circular if thesemiconductor light-emitting diodes are circular. Further, each cell isconfigured to accommodate one semiconductor light-emitting diode. Thatis, one cell accommodates one semiconductor light-emitting diode.

Meanwhile, the plurality of electrodes 161 c have a plurality ofelectrode lines that are placed at the bottom of the cells 161 d, andthe electrode lines can be configured to extend to neighboring cells.

The electrodes 161 c are placed on the undersides of the cells 161 d,and different polarities can be applied to create an electric fieldwithin the cells 161 d. To form an electric field, the dielectric layer161 b can form the bottom of the cells 161 d while covering theelectrodes 161 c. With this structure, when different polarities areapplied to a pair of electrodes 161 c on the underside of each cell 161d, an electric field is formed and the semiconductor light-emittingdiodes can be inserted into the cells 161 d by the electric field.

The electrodes of the substrate 161 at the assembly site areelectrically connected to a power supply 171. The power supply 171performs the function of generating an electric field by applying powerto the electrodes.

As shown in the drawings, the self-assembly device can have magnets 163for applying magnetic force to the semiconductor light-emitting diodes.The magnets 163 are placed at a distance from the assembly chamber 162and apply a magnetic force to the semiconductor light-emitting diodes150. The magnets 163 can be placed to face the opposite side of theassembly surface of the substrate 161, and the positions of the magnets163 are controlled by the position controller 164 connected to themagnets 163.

The semiconductor light-emitting diodes 1050 can have a magneticmaterial so that they are moved within the fluid by a magnetic field.

Referring to FIG. 9, a semiconductor light-emitting diode having amagnetic material can comprise a first conductive electrode 1052, asecond conductive electrode 1056, a first conductive semiconductor layer1053 where the first conductive electrode 1052 is placed, a secondconductive semiconductor layer 1055 which overlaps the first conductivesemiconductor layer 1053 and where the second conductive semiconductorlayer 1055 is placed, and an active layer 1054 placed between the firstand second conductive semiconductor layers 1053 and 1055.

Here, the first conductive can refer to p-type, and the secondconductive type can refer to n-type, or vice versa. As statedpreviously, the semiconductor light-emitting diode can be formed withoutthe active layer.

Meanwhile, in the present disclosure, the first conductive electrode1052 can be formed after the semiconductor light-emitting diode isassembled onto the wiring substrate by the self-assembling of thesemiconductor light-emitting diode. Further, in the present disclosure,the second conductive electrode 1056 can comprise a magnetic material.The magnetic material can refer a magnetic metal. The magnetic materialcan be Ni, SmCo, etc. In another example, the magnetic material caninclude at least one among Gd-based, La-based, and Mn-based materials.

The magnetic material can be provided in the form of particles on thesecond conductive electrode 1056. Alternatively, one layer of aconductive electrode comprising a magnetic material can be composed ofthe magnetic material. An example of this is the second conductiveelectrode 1056 of the semiconductor light-emitting diode 1050 whichcomprises a first layer 1056 a and a second layer 1056 b, as shown inFIG. 9. Here, the first layer 1056 a can comprise a magnetic material,and the second layer 1056 b can comprise a metal material other than themagnetic material.

As shown in the drawing, in this example, the first layer 1056 acomprising the magnetic material can be placed in contact with thesecond conductive semiconductor layer 1055. In this case, the firstlayer 1056 a is placed between the second layer 1056 b and the secondconductive semiconductor layer 1055. The second layer 1056 b can be acontact metal that is connected to the wiring electrode on the wiringsubstrate. However, the present disclosure is not necessarily limited tothis, and the magnetic material can be placed on one surface of thefirst conductive semiconductor layer.

Referring again to FIGS. 6 and 7, more specifically, on top of theassembly chamber of the self-assembly device, a magnet handler (ormagnetic handler) capable of automatically or manually moving themagnets 163 on the x, y, and z axes or a motor capable of rotating themagnets 163 can be provided. The magnet handler and motor can constitutethe position controller 164. As such, the magnets 163 can rotate in ahorizontal, clockwise, or counterclockwise direction to the substrate161.

Meanwhile, the assembly chamber 162 can be formed with alight-transmissive bottom plate 166, and the semiconductorlight-emitting diodes can be placed between the bottom plate 166 and thesubstrate 161. An image sensor 167 can be placed opposite to the bottomplate 166 so as to monitor the inside of the assembly chamber 162through the bottom plate 166. The image sensor 167 can be controlled bya controller 172, and can come with an inverted-type lens, CCD, etc. soas to observe the assembly surface of the substrate 161.

The above-described self-assembly device is configured to use a magneticfield and an electric field in combination. With this, the semiconductorlight-emitting diodes are mounted at preset positions on the substrateby an electric field while in the process of being moved by changes inthe positions of the magnets. Below, the assembly process using theabove-described self-assembly device will be described in more details.

First of all, a plurality of semiconductor light-emitting diodes 1050having a magnetic material can be formed through the process explainedwith reference to FIGS. 5A to 5C. In this case, the magnetic materialcan be deposited onto the semiconductor light-emitting didoes in theprocess of forming the second conductive electrode of FIG. 5C.

Next, the substrate 161 is fed to an assembly site, and thesemiconductor light-emitting diodes 1050 are put into the assemblychamber 162 (see FIG. 8A).

As described above, the assembly site on the substrate 161 can be aposition at which the substrate 161 is placed in the assembly chamber162 in such a way that an assembly surface where the semiconductorlight-emitting diodes 150 are assembled faces downwards.

In this case, some of the semiconductor light-emitting diodes 1050 cansink to the bottom of the assembly chamber 162 and some of them canfloat in the fluid. If the assembly chamber 162 comes with alight-transmissive bottom plate 166, some of the semiconductorlight-emitting diodes 1050 can sink to the bottom plate 166.

Next, a magnetic force is applied to the semiconductor light-emittingdiodes 1050 so that the semiconductor light-emitting diodes 1050 in theassembly chamber 162 come up to the surface (see FIG. 8B).

When the magnets 163 of the self-assembly device move to the oppositeside of the assembly surface of the substrate 161 from their originalpositions, the semiconductor light-emitting diodes 1050 float in thefluid towards the substrate 161. The original positions can refer topositions at which the magnets 163 are outside the assembly chamber 162.In another example, the magnets 163 can be composed of electromagnets.In this case, an initial magnetic force is generated by supplyingelectricity to the electromagnets.

Meanwhile, in this embodiment, the assembly surface of the substrate 161and the spacing between the semiconductor light-emitting diodes 1050 canbe controlled by adjusting the strength of the magnetic force. Forexample, the spacing is controlled by using the weight, buoyancy, andmagnetic force of the semiconductor light-emitting diodes 1050. Thespacing can be several millimeters to several tens of micrometers fromthe outermost part of the substrate 161.

Next, a magnetic force is applied to the semiconductor light-emittingdiodes 1050 so that the semiconductor light-emitting diodes 1050 move inone direction within the assembly chamber 162. For example, the magnets163 can move in a horizontal, clockwise, or counterclockwise directionto the substrate 161 (see FIG. 8C). In this case, the semiconductorlight-emitting diodes 1050 are moved horizontally to the substrate 161by the magnetic force, spaced apart from the substrate 161.

Next, the semiconductor light-emitting diodes 1050 are guided to presetpositions on the substrate 161 by applying an electric field so that thesemiconductor light-emitting diodes 1050 are mounted at the presetpositions while in the process of being moved (see FIG. 8C). Forexample, the semiconductor light-emitting diodes 1050 are movedvertically to the substrate 161 by the electric field and mounted atpreset positions on the substrate 161, while being moved horizontally tothe substrate 161.

More specifically, an electric field is generated by supplying power tobi-planar electrodes on the substrate 161, and the semiconductorlight-emitting diodes 1050 are guided to the preset positions andassembled only there by the electric field. That is, the semiconductorlight-emitting diodes 1050 are self-assembled at an assembly site on thesubstrate 161 by a selectively generated electric field. To this end,the substrate 161 can be formed with cells into which the semiconductorlight-emitting diodes 1050 are fitted.

Afterwards, the unloading of the substrate 161 is performed, therebycompleting the assembly process. In a case where the substrate 161 is anassembly substrate, an array of semiconductor light-emitting diodes canbe transferred onto a wiring substrate to carry out a subsequent processfor realizing the display device, as described previously.

Meanwhile, after the semiconductor light-emitting diodes 1050 are guidedto the preset positions, the magnets 163 can be moved in a direction inwhich they get farther away from the substrate 161, so that thesemiconductor light-emitting diodes 1050 remaining in the assemblychamber 162 fall to the bottom of the assembly chamber 162 (see FIG.8D). In another example, if power supply is stopped in a case where themagnets 163 are electromagnets, the semiconductor light-emitting diodes1050 remaining in the assembly chamber 162 fall to the bottom of theassembly chamber 162.

Thereafter, the semiconductor light-emitting diodes 1050 on the bottomof the assembly chamber 162 can be collected, and the collectedsemiconductor light-emitting diodes 1050 can be re-used.

In the above-described self-assembly device and method, parts distantfrom one another are concentrated near a preset assembly site by using amagnetic field in order to increase assembly yields in a fluidicassembly, and the parts are selectively assembled only at the assemblysite by applying an electric field to the assembly site. In this case,the assembly substrate is positioned on top of a water tank, with itsassembly surface facing downward, thus minimizing the effect of gravityfrom the weights of the parts and avoiding non-specific binding andeliminating defects.

As seen from above, with the above configuration according to thepresent disclosure, large numbers of semiconductor light-emitting diodescan be assembled at a time on a display device where individual pixelsare made up of semiconductor light-emitting diodes.

As such, according to the present disclosure, large numbers ofsemiconductor light-emitting diodes can be pixelated on a small-sizedwafer and then transferred onto a large-area substrate. This enables themanufacture of a large-area display device at a low cost.

When the self-assembly process described above is performed, severalproblems occur.

Firstly, as an area of the display increases, an area of the assemblysubstrate increases. As the area of the assembly substrate increases,there is a problem that a warpage phenomenon of the substrate increasesdue to a weight of the assembly substrate. When a self-assembly isperformed in a state in which the assembly substrate is warped, sincethe magnetic field at the surface of the assembly substrate is notuniformly formed, it is difficult to perform the self-assembly stably.

Secondly, since the semiconductor light-emitting diodes may not becompletely uniformly dispersed in the fluid and the magnetic fieldformed at the surface of the assembly substrate may not be uniformcompletely, a problem that the semiconductor light-emitting diodes areconcentrated only at a partial region of the assembly substrate canoccur.

The present disclosure provides a self-assembly device capable ofsolving the above-described problems and increasing a self-assemblyyield.

The self-assembly device according to the present disclosure can includea substrate surface treatment part, a substrate chuck 200, a magneticfield forming part 300, a chip supply part 400, and an assembly chamber500. However, the present disclosure is not limited thereto, and theself-assembly device according to the present disclosure can includemore or less components than those described above.

Prior to describing the self-assembly device according to the presentdisclosure, a method for self-assembly using the self-assembly deviceaccording to the present disclosure will be described briefly.

FIG. 10 is a flowchart showing a method for self-assembly according tothe present disclosure.

First, a surface treatment step S110 of an assembly substrate isperformed. The step is not essential, but when a surface of thesubstrate is hydrophilized, it is possible to prevent bubbles from beinggenerated on the surface of the substrate.

Next, a step S120 of loading the assembly substrate onto the substratechuck is performed. The assembly substrate loaded on the substrate chuck200 is transferred to an assembly position of the assembly chamber.Thereafter, the magnetic field forming part approaches the assemblysubstrate through vertical and horizontal movements.

In such a state, a step S130 of supplying a chip is performed.Specifically, a step of dispersing the semiconductor light-emittingdiode on the assembly surface of the assembly substrate is performed.When the semiconductor light-emitting diode is dispersed near theassembly surface in a state in which the magnetic field forming part 300is close enough to the assembly substrate, the semiconductorlight-emitting diodes adhere to the assembly surface by the magneticfield forming part. The semiconductor light-emitting diodes aredispersed onto the assembly surface at an appropriate dispersion.

However, the present disclosure is not limited thereto, and thesemiconductor light-emitting diode can be dispersed into the fluid inthe assembly chamber before the substrate is transferred to the assemblyposition. That is, a time point at which the chip supply step S130 isperformed is not limited to after the assembly substrate is transferredto the assembly position.

A method of supplying the semiconductor light-emitting diode can varyaccording to an area of the assembly substrate, a type of thesemiconductor light-emitting diode to be assembled, and a self-assemblyspeed.

Thereafter, a step S140 of performing the self-assembly and collectingthe semiconductor light-emitting diode is performed. The self-assemblywill be described later together with a description of a self-assemblydevice according to the present disclosure. Meanwhile, the semiconductorlight-emitting diode is not necessarily collected after theself-assembly. After the self-assembly is completed, the semiconductorlight-emitting diode in the assembly chamber is replenished, and then anew substrate can be used to self-assemble the semiconductorlight-emitting diode.

Lastly, after the self-assembly is completed, a step S150 of inspectingand drying the assembly substrate, and separating the substrate from thesubstrate chuck can be performed. The inspection of the assemblysubstrate can be performed at the position in which the self-assemblyhas been performed, and can be performed after the assembly substrate istransferred to another position.

Meanwhile, the drying of the assembly substrate can be performed afterthe assembly substrate is separated from the fluid. After the drying ofthe assembly substrate, a post process of the self-assembly can beperformed.

Contents of a basic principle of the self-assembly, a structure of thesubstrate (or assembly substrate), and the semiconductor light-emittingdiode are replaced with those described in FIGS. 1 to 9. Meanwhile,since a vertical moving part, a horizontal moving part, a rotating part,and other moving means described below can be implemented throughseveral known means such as a motor and a ball screw, a rack gear and apinion gear, and a pulley and a timing belt, and the like, detaileddescriptions thereof will be omitted.

Meanwhile, the controller 172 described in FIG. 7 controls movements ofthe vertical moving part, the horizontal moving part, the rotating part,and other moving means provided in the above-described components. Thatis, the controller 172 is configured to control movements of x, y, and zaxes and a rotating movement of each component. Even though notmentioned separately in the specification, the movements of the verticalmoving part, the horizontal moving part, the rotating part, and othermoving means are generated by the control of the controller 172.

Meanwhile, the electrode 161 c provided at the substrate (or assemblysubstrate 161) described in FIGS. 6 to 9 is referred to as an assemblyelectrode, the assembly electrode 161 c is electrically connected to thepower supply 171 described in FIG. 7 via the substrate chuck 200, andthe power supply 171 supplies power to the assembly electrode 161 c bythe control of the controller 172. Detailed description thereof will bedescribed later.

Hereinafter, the above-described components will be described.

First, a substrate surface treatment part serves to hydrophilize asubstrate surface. Specifically, the self-assembly device according tothe present disclosure performs a self-assembly in a state in which theassembly substrate is in contact with a fluid surface. When the assemblysurface of the assembly substrate has a heterogeneous property with thefluid surface, bubbles and the like can occur at the assembly surface,and non-specific coupling between the semiconductor light-emitting diodeand the assembly surface can occur. To prevent this, the substratesurface can be treated with fluid-friendly properties before theself-assembly.

In one embodiment, when the fluid is a polar material such as water, thesubstrate surface treatment part can hydrophilize the assembly surfaceof the substrate.

For example, the substrate surface treatment part can include a plasmagenerator. Hydrophilic functional groups can be formed at the substratesurface by plasma treatment of the substrate surface. Specifically, thehydrophilic functional groups can be formed at at least one of apartition wall and a dielectric layer provided at the substrate by theplasma treatment.

Meanwhile, different surface treatments can be performed at a partitionwall surface and a surface of the dielectric layer exposed to theoutside by a cell so as to prevent non-specific coupling of thesemiconductor light-emitting diode. For example, a hydrophilic treatmentcan be performed at the surface of the dielectric layer exposed to theoutside by the cell, and a surface treatment can be performed to formhydrophobic functional groups at the surface of the partition wall.Accordingly, non-specific coupling of the semiconductor light-emittingdiode with respect to the surface of the partition wall can beprevented, and the semiconductor light-emitting diode can be stronglyfixed inside the cell.

However, the substrate surface treatment part is not an essentialcomponent in the self-assembly device according to the presentdisclosure. The substrate surface treatment part need not be necessarydepending on a material configuring the substrate.

The substrate at which the surface treatment is completed by thesubstrate surface treatment part is loaded onto a substrate chuck 200.

Next, the substrate chuck 200 will be described.

FIG. 11 is a conceptual diagram showing a first state of a substratechuck, FIG. 12 is a conceptual diagram showing a second state of thesubstrate chuck, FIG. 13 is a plan view of a first frame provided at thesubstrate chuck, and FIG. 14 is a conceptual diagram showing a state inwhich an assembly substrate is loaded at the substrate chuck.

Referring to the accompanying drawings, the substrate chuck 200 includesa substrate support part (or substrate support) 205. In one embodiment,the substrate support part 205 can include first and second frames 210and 220 and a fixing part 230. The first and second frames 210 and 220are disposed at upper and lower sides of the loaded substrate interposedtherebetween, and the fixing part 230 supports the first and secondframes 210 and 220. The substrate chuck 200 can include all of arotating part 240, a vertical moving part (or a vertical mover), and ahorizontal moving part (or a horizontal mover). As shown in FIG. 11, thevertical moving part and the horizontal moving part can be formed as onedevice as a moving part 250, but such is not required, and the verticalmoving part and the horizontal moving part may can be formed separately.Meanwhile, the present disclosure is not limited to drawings describedbelow, and the rotating part, the vertical and horizontal moving partsprovided at the substrate chuck can be formed as one device.

In the present specification, the first frame 210 is defined as a framedisposed at a lower side of the substrate in a state in which theassembly surface of the substrate S faces a fluid, and the second frame220 is defined as a frame disposed at a upper side of the substrate in astate in which the assembly surface of the substrate faces the fluid.The upper and lower sides relation between the first frame 210 and thesecond frame 220 can be switched with each other due to the rotatingpart 240. In the present specification, a state in which the first frame210 is under the second frame 220 is defined as a first state (see FIG.11), and a state in which the first frame 210 is over the second frame220 is defined as a second state (see FIG. 12). The rotating part 240rotates at least one of the first and second frames 210 and 220 and thefixing part 230 to switch from any one of the first and second states tothe other. The rotating part 240 will be described later.

The first frame 210 is a frame in contact with the fluid filled in theassembly chamber during self-assembly. Referring to FIG. 14, the firstframe 210 includes a bottom portion 210′ and a sidewall portion 210″.

The bottom portion 210′ serves to support the substrate at the lowerside or the upper side of the substrate S when the substrate S isloaded. The bottom portion 210′ can be formed in one plate shape, or canbe formed in a form in which a plurality of members forming a plateshape are coupled to each other. Referring to FIG. 13, the bottomportion 210′ includes a hole 210′″ passing through a central portion.The hole 210′″ can expose a substrate which will be described later tothe outside to be in contact with the fluid. That is, the hole 210′″defines the assembly surface of the substrate. The substrate is loadedsuch that four corners of the rectangular substrate are mounted on anedge of the hole 210′″ of the first frame 210. Accordingly, a remainingregion except the edge of the substrate is overlapped with the hole210′″ provided at the first frame 210. The region of the substrateoverlapped with the hole 210′″ becomes an assembly surface. Buoyancy (orupthrust), is a force (e.g., upward) exerted by a fluid that opposes theweight of an immersed object, such as the substrate support part 205. Inthis context, the hole 210′″ is an area of the first frame 210 (e.g., ofthe bottom portion 210′) that does not directly support a surface of thesubstrate S. Accordingly, when the substrate support part 205 is placedon or partially immersed in the fluid, a force is applied (e.g., by thefluid due to pressure difference between air on one side and the fluidon another side of the substrate S) to a portion of the substrate S thatis over the hole 210′″, the substrate S becomes pushed (or pulled) sothat the substrate S goes from a curved state under its own weight(without support or buoyancy from the fluid) to a flat state (oroppositely curved state) due to support or due to a counterforce to theweight from buoyancy or pressure that is difference from that of thefluid.

Meanwhile, a sealing part 212 and an electrode connection part 213 canbe disposed adjacent the edge of the hole 210′″, and can be arrangedparallel to the edge of the hole 210′″.

The sealing part 212 is in close contact with the substrate to preventthe fluid filled in the assembly chamber from penetrating into the firstand second frames 210 and 220 during self-assembly. In addition, thesealing part 212 prevents the fluid from penetrating into the assemblyelectrode 161 c and the electrode connection part 213. For this, thesealing part 212 should be disposed at a position closer to the hole210′″ than the electrode connection part 213.

The sealing part 212 is formed in a ring shape, and a material of thesealing part 212 is not particularly limited. The material forming thesealing part 212 can be a known sealing material.

The electrode connection part 213 is connected to the assembly electrodeformed at the substrate to supply a power to the assembly electrode. Inone embodiment, the electrode connection part 213 can apply a powersupplied from the power supply 171 described in FIG. 7 to the assemblyelectrode 161 c to form an electric field on the substrate.

Meanwhile, the sidewall portion 210″ is formed at an edge of the bottomportion 210′. The sidewall portion 210″ prevents the fluid frompenetrating into an opposite surface of the assembly surface of thesubstrate during self-assembly. Specifically, the self-assembly deviceaccording to the present disclosure performs self-assembly in a state inwhich the substrate is submerged in the fluid. The sidewall portion 210″prevents the fluid from penetrating into the opposite surface of theassembly surface of the substrate when the substrate is submerged in thefluid.

For this, the sidewall portion 210″ is formed to surround an entire edgeof the substrate. A height of the sidewall portion 210″ should begreater than a depth at which the substrate is submerged in the fluid.The sidewall portion 210″ prevents the fluid from penetrating into theopposite surface of the assembly surface of the substrate, and thus thesubstrate is prevented from being damaged, and buoyancy of the fluid isapplied to only one surface of the substrate. This will be describedlater.

Meanwhile, the second frame 220 serves to press the substrate at theopposite side of the first frame 210 during self-assembly. Like thefirst frame 210, the second frame 220 includes a hole passing through acentral portion. The hole formed at the second frame 220 is formed tohave a size equal to or larger than the hole 210′″ formed at the firstframe 210.

The hole formed at the second frame 220 allows the opposite surface ofthe assembly surface of the substrate to be exposed to the outside. Theopposite surface of the assembly surface of the substrate should beexposed to the outside in the same area as the assembly surface or in alarger area than the assembly surface. This is because the magneticfield forming part 300 forms a magnetic field at the opposite side ofthe assembly surface of the substrate. The opposite surface of theassembly surface of the substrate should be exposed to the outside suchthat the magnetic field forming part 300 can sufficiently approach thesubstrate.

Meanwhile, the substrate S is loaded between the first and second frames210 and 220 in the second state. Accordingly, the substrate S is slidand loaded at one surface of the second frame 220. A protrusion forguiding an alignment position of the substrate can be formed at at leastone of the first and second frames such that the substrate is aligned toa correct position. In one embodiment, referring to FIG. 13, aprotrusion 211 guiding the alignment position of the substrate S can beformed at the first frame 210.

Meanwhile, when the substrate S is loaded on the second frame 220, atleast one of the first and second frames 210 and 220 moves verticallysuch that the first and second frames 210 and 220 press the substrate.For this, the substrate chuck 200 can include a frame moving partdisposed at at least one of the fixing part 230, and the first and thesecond frames 210 and 220. At this time, the sealing part 212 pressesthe substrate S.

In one embodiment, a frame moving part for vertically moving the secondframe 220 can be disposed at the fixing part 230. While the substratechuck is in the second state, when the substrate S is loaded on thesecond frame 220, the vertical moving part moves the second frame 220upwardly such that the substrate S can be strongly fixed between thefirst and second frames 210 and 220. At this time, the electrodeconnection part 213 provided at the first frame 210 is connected to theassembly electrode of the substrate S, and the sealing part 212 providedat the first frame 210 presses the edge of the substrate S. In thisstate, when the substrate chuck switches to the first state, thesubstrate chuck has a shape as shown in FIG. 14.

However, the present disclosure is not limited thereto, and the framemoving part can be formed so as to move any one of the first and secondframes 210 and 220 horizontally with respect to the other. In this case,the frame moving part is formed so as to move any one of the first andsecond frames 210 and 220 vertically and horizontally with respect tothe other. When any one of the first and second frames 210 and 220 canbe moved horizontally with respect to the other, a connection partbetween the electrode connection part 213 and the assembly electrode canbe changed. It can be used to detect whether the assembled electrode isdefective.

Meanwhile, the rotating part 240 is disposed at one side of the fixingpart 230 provided at the substrate chuck 200 described above. Therotating part 240 rotates the fixing part 230 such that the upper andlower-sides relation of the first and second frames 210 and 220 can beswitched to each other. The substrate chuck 200 is switched from any oneof the first and second states to the other by rotating movement of therotating part 240. A rotation speed, a degree of rotation, a rotationdirection, and the like of the rotating part 240 can be controlled bythe controller 172 described in FIG. 7.

In one embodiment, the substrate chuck 200 is in the second state beforethe substrate S is loaded, and the controller 172 controls the rotatingpart 240 to rotate the fixing part 230 to 180 degrees after thesubstrate S is loaded such that the substrate chuck 200 is switched tothe first state.

Meanwhile, a vertical moving part and a horizontal moving part aredisposed at one side of the fixing part 230.

The horizontal moving part moves at least one of the fixing part 230,and the first and second frames 210 and 220 such that the assemblysurface of the substrate can be aligned at an open position of theassembly chamber after the substrate is loaded.

The vertical moving part moves at least one of the fixing part 230, andthe first and second frames 210 and 220 such that the vertical distancebetween the substrate and the assembly chamber is adjusted. A warpagephenomenon of the substrate S can be corrected or compensated by thevertical moving part using the buoyancy. This will be described later.

In summary, the substrate S is loaded in the second state of thesubstrate chuck 200 (see FIG. 12). Thereafter, the substrate chuck 200is switched to the first state (see FIG. 11) and then aligned with theassembly chamber. In this process, the substrate chuck 200 movesvertically and horizontally such that the assembly surface of thesubstrate S is in contact with the fluid filled in the assembly chamber.Thereafter, the controller 172 controls the magnetic field forming part300.

Next, the magnetic field forming part 300 will be described.

FIG. 15 is a perspective view of a magnetic field forming part accordingto one embodiment of the present disclosure, FIG. 16 is one side view ofa magnetic field forming part according to one embodiment of the presentdisclosure, FIG. 17 is a bottom side view of a magnetic field formingpart according to one embodiment of the present disclosure, and FIG. 18is a conceptual diagram showing a trajectory of magnets provided at amagnetic field forming part according to the present disclosure.

Referring to the drawings, the magnetic field forming part 300 includesa magnet array 310, a vertical moving part 320, a horizontal moving part320, and a rotating part 320. The magnetic field forming part 300 isdisposed at an upper side of the assembly electrode to serve to form amagnetic field.

Specifically, the magnet array 310 includes a plurality of magnets 313.The magnet 313 provided at the magnet array 310 can be a permanentmagnet or an electromagnet. The magnets 313 serves to form a magneticfield so that the semiconductor light-emitting diodes are led to theassembly surface of the substrate.

The magnet array 310 can include a support part 311 and a magnet movingpart 312. The support part 311 is connected to parts 320 that caninclude a vertical moving part, a horizontal moving part, and a rotatingpart.

Meanwhile, one end of the magnet moving part 312 is fixed to the supportpart 311, and the magnet 313 is fixed to the other end of the magnetmoving part 312. The magnet moving part 312 is formed to be stretchablein length, and as the magnet moving part 312 is stretched, a distancebetween the magnet 313 and the support part 311 changes.

As shown in the accompanying drawings, the magnet moving part 312 can beconfigured to vertically move the magnets 313 disposed in one row at atime. In this case, the magnet moving part 312 can be disposed for eachcolumn of the magnet array.

On the other hand, the magnet moving part 312 can be disposed by thenumber of magnets provided in the magnet array. Accordingly, a distancebetween each of a plurality of magnets and the support part can beadjusted differently.

The plurality of magnet moving parts serves to adjust finely a gapbetween the magnet 313 and the substrate S, and when the substrate iswarped, serves to adjust uniformly the gaps between the magnets 313 andthe substrate S. Self-assembly can be performed in a state in which themagnet 313 is in contact with the substrate S, or can be performed in astate in which the magnet 313 is spaced apart from the substrate S at apredetermined distance.

Meanwhile, the horizontal moving part can include a rotating part. Whenthe self-assembly is performed, the horizontal moving part provided atthe magnetic field forming part 300 moves the magnet in one directionand rotates the magnet, simultaneously. Accordingly, the magnet array310 rotates with respect to a predetermined rotation axis and movesalong one direction, simultaneously. For example, referring to FIG. 18,the magnet 313 provided at the magnet array 310 can move while drawing atrajectory P mixed with a curved line and a straight line.

The semiconductor light-emitting diode can be supplied in a state inwhich the magnetic field forming part 300 is close to the substrate Swithin a predetermined distance.

FIG. 19 is a conceptual diagram showing a state in which a semiconductorlight-emitting diode is supplied.

Referring to FIG. 19, a chip supply part 400 can be disposed in anassembly chamber 500 to be described later. The substrate S is alignedwith the assembly chamber 500, and then the chip supply part 400 servesto supply the semiconductor light-emitting diode to the assembly surfaceof the substrate S. Specifically, the chip supply part 400 can include achip accommodating part that can accommodate a chip at an upper portionthereof, a vertical moving part, and a horizontal moving part. Thevertical and horizontal moving parts allow the chip accommodating partto move in the fluid filled in the assembly chamber.

The plurality of semiconductor light-emitting diodes can be loaded atthe chip accommodating part. After the substrate is aligned with theassembly chamber, when the magnetic field forming part 300 is broughtclose to the substrate within a predetermined distance, a magnetic fieldof a predetermined intensity or more is formed on the assembly surface.In this state, when the chip accommodating part is brought close to theassembly surface within the predetermined distance, the semiconductorlight-emitting diodes loaded at the chip accommodating part are incontact with the substrate. The vertical moving part provided at thechip supply part brings the chip accommodating part close to a partialregion of the assembly surface of the substrate within the predetermineddistance through vertical movement.

After a predetermined time passes, the vertical moving part provided atthe chip supply part allows the chip accommodating part to be separatedfrom the partial region of the assembly surface of the substrate at thepredetermined distance or longer through vertical movement. Thereafter,the horizontal moving part provided at the chip supply part moveshorizontally the chip accommodating part such that the chipaccommodating part is overlapped with a different region from thepartial region of the assembly surface. Thereafter, the vertical movingpart provided at the chip supply part brings the chip accommodating partclose to the different region within the predetermined distance throughvertical movement. By repeating such a process, the chip supply partbrings the plurality of semiconductor light-emitting diodes into contactwith an entire region of the assembly surface of the substrate.Self-assembly can be performed in a state in which the plurality ofsemiconductor light-emitting diodes are constantly dispersed and incontact with the entire region of the assembly surface of the substrate.

As described above, there are largely two problems in self-assembly. Asecond problem is that since the semiconductor light-emitting diodesneed not be completely uniformly dispersed in the fluid and the magneticfield formed at the surface of the assembly substrate need not beperfectly uniform, there is a problem that the semiconductorlight-emitting diodes are concentrated only at a partial region of theassembly substrate. When using the chip supply part 400 described above,it is possible to solve the second problem described above.

However, the present disclosure is not limited thereto, and the chipsupply part is not an essential component of the present disclosure.Self-assembly can be performed in a state in which the semiconductorlight-emitting diode is dispersed in the fluid, or in a state in whichthe plurality of semiconductor light-emitting diodes are dispersed andin contact with the assembly surface of the substrate by another partwhich is not the chip supply part.

Next, the assembly chamber 500 will be described.

FIG. 20 is a plan view of an assembly chamber according to oneembodiment of the present disclosure, FIG. 21 is a cross-sectional viewtaken along line A-A′ of FIG. 20, and FIGS. 22 and 23 are conceptualdiagrams showing a movement of a gate provided at an assembly chamberaccording to one embodiment of the present disclosure.

The assembly chamber 500 includes a space for accommodating a pluralityof semiconductor light-emitting diodes. The space can be filled with afluid, and the fluid can include water, and the like as an assemblysolution. Therefore, the assembly chamber 500 can be a water tank, andcan be configured as an open type. However, the present disclosure isnot limited thereto, and the space of the assembly chamber 500 can be aclosed type formed in a closed space.

In the assembly chamber 500, a substrate S is disposed such that anassembly surface at which the semiconductor light-emitting diodes 150are assembled is faced downwardly. For example, the substrate S istransferred to an assembly position by the substrate chuck 200.

At this time, the assembly surface of the substrate S at the assemblyposition faces a bottom of the assembly chamber 500. Accordingly, theassembly surface is toward a direction of gravity. The assembly surfaceof the substrate S is disposed to be submerged in the fluid in theassembly chamber 500.

In one embodiment, the assembly chamber 500 can be divided into tworegions. Specifically, the assembly chamber 500 can be divided into anassembly region 510 and an inspection region 520. In the assembly region510, the semiconductor light-emitting diode disposed in the fluid isassembled to the substrate S in a state in which the substrate S issubmerged in the fluid.

On the other hand, in the inspection region 520, the substrate S thathas been self-assembled is inspected. Specifically, the substrate S isassembled at the assembly region and then transferred to the inspectionregion via the substrate chuck.

The same fluid can be filled in the assembly region 510 and theinspection region 520. The substrate can be transferred from theassembly region to the inspection region in a state in which thesubstrate is submerged in the fluid. When the substrate S disposed inthe assembly region 510 is taken out of the fluid, the previouslyassembled semiconductor light-emitting diode can be separated from thesubstrate due to surface energy between the fluid and the semiconductorlight-emitting diode. For this reason, it is preferable that thesubstrate is transferred in a state of being submerged in the fluid.

The assembly chamber 500 can include a gate 530 configured to be capableof moving up and down such that the substrate can be transferred in astate of being submerged in the fluid. As shown in FIG. 22, the gate 530maintains an elevated state (first state) during self-assembly or duringsubstrate inspection, so that the fluid accommodated in the assemblyregion 510 and the inspection region 520 of the assembly chamber 500 isseparated from each other. The gate 530 separates the assembly regionand the inspection region, thereby preventing disturbing the inspectionof the substrate due to moving of the semiconductor light-emitting diodeto the inspection region during self-assembly.

As shown in FIG. 23, when the substrate S is transferred, the gate 530moves down (second state) to remove a boundary between the assemblyregion 510 and the inspection region 520. Accordingly, the substratechuck 200 can transfer the substrate from the assembly region 510 to theinspection region 520 by only horizontal movement without separatevertical movement.

Meanwhile, a sonic generator for preventing agglomeration of thesemiconductor light-emitting diode can be disposed at the assemblyregion 510. The sonic generator can prevent the plurality ofsemiconductor light-emitting diodes from agglomerating with each otherby vibration.

Meanwhile, bottom surfaces of the assembly region 510 and the inspectionregion 520 can be made of a light transmissive material. In oneembodiment, referring to FIG. 20, light transmission regions 511 and 512can be provided at the bottom surfaces of the assembly region 510 andthe inspection region 520, respectively. Accordingly, the presentdisclosure enables to monitor the substrate during self-assembly, or toperform inspection with respect to the substrate. It is preferable thatan area of the light transmission region is larger than that of theassembly surface of the substrate. However, the present disclosure isnot limited thereto, and the assembly chamber can be configured toperform self-assembly and inspection at the same position.

When using the substrate chuck 200, the magnetic field forming part 300,and the assembly chamber 500 as described above, the self-assemblydescribed in FIGS. 8A to 8E can be performed. Hereinafter, a detailedstructure and method for solving problems caused during self-assemblywill be described in detail.

First, a structure and method for solving the most critical problem thatoccurs during self-assembly will be described. When describing theproblem in detail, as an area of a display increases, an area of anassembly substrate increases, and as the area of the assembly substrateincreases, a problem that a warpage phenomenon of the substrateincreases occurs. When performing self-assembly in a state in which theassembly substrate is warped, since a magnetic field is not uniformlyformed or applied at a surface of the assembly substrate, it isdifficult to perform the self-assembly stably.

FIG. 24 is a conceptual diagram showing a substrate warpage phenomenoncaused during self-assembly.

Referring to FIG. 24, when a substrate S maintains a flat state duringself-assembly, a distance between a plurality of magnets 313 and thesubstrate S can be uniform. In this case, a magnetic field can be formeduniformly at an assembly surface of the substrate. However, when thesubstrate is actually loaded onto the substrate chuck 200, the substrateis warped due to gravity. In a warped substrate S′, since a distancebetween the plurality of magnets 313 and the substrate S′ is notconstant, uniform self-assembly is difficult. Since a magnetic fieldforming part is disposed on an upper side of the substrate, a separateinstrument for correcting the warpage phenomenon of the substrate isdifficult to be disposed on the upper side of the substrate. Inaddition, when the separate instrument for correcting the warpagephenomenon of the substrate is disposed on a lower side the substrate,movement of the semiconductor light-emitting diodes can be restricted,and there is a problem that the instrument covers a part of the assemblysurface. For this reason, it is difficult to dispose the instrument forcorrecting the warpage phenomenon of the substrate either on the upperside or the lower side of the substrate.

The present disclosure provides a structure and method of a substratechuck for correcting a warpage phenomenon of the substrate.

FIG. 25 is a conceptual diagram showing a method for correcting awarpage phenomenon of a substrate.

Referring to FIG. 25, after loading a substrate S′ at a substrate chuck200, when an assembly surface of the substrate faces the gravitydirection, the substrate S′ is warped. In order to minimize warping ofthe substrate when loading the substrate, at least one of first andsecond frames 210 and 220 provided at the substrate chuck appliespressure to all four corners of a rectangular substrate. Nevertheless,when the area of the substrate S′ is increased, the substrate isinevitably warped due to gravity.

As shown in the second drawing of FIG. 25, after the substrate chuck 200is moved to an assembly position, when the substrate chuck 200 is moveddown at a predetermined distance, the substrate S′ brings into contactwith a fluid F. In a state in which the substrate S′ is simply incontact with the fluid F, the warpage phenomenon of the substrate S′ isnot corrected. Although self-assembly can be performed in a state asshown in the second drawing of FIG. 25, it is difficult to performuniform self-assembly.

The present disclosure further moves down the substrate chuck 200 in thestate in which the substrate S′ is in contact with the fluid F in orderto correct the warpage phenomenon of the substrate. At this time, asealing part 212 provided at the first frame 210 prevents the fluid Ffrom penetrating into a window of the first frame. In addition, asidewall portion 210″ provided at the first frame 210 prevents the fluidF from flowing over the first frame to an opposite surface of theassembly surface of the substrate S′.

Here, the sealing part 212 should be formed to surround all edges of thesubstrate. In addition, a height of the sidewall portion 210″ should begreater than a depth at which the first frame 210 is moved down to themaximum based on a state in which the first frame 210 is in contact withthe fluid F. That is, when the substrate chuck 200 moves down, the fluidshould not penetrate over the window and the sidewall portion 210″ ofthe first frame 210.

When the substrate chuck 200 moves down, a surface of the fluid F israised due to the sealing part 212 and the sidewall portion 210″ asdescribed above. At this time, buoyancy by the fluid F acts on thesubstrate S′. As the surface rising width of the fluid F increases, thebuoyancy acting on the substrate S′ increases.

In the present disclosure, the buoyancy (and thereby an amount of force)acting on the substrate can be changed by measuring or determining adegree of warping of the substrate S′ and adjusting a descending widthof the substrate chuck 200 according to the degree of warping of thesubstrate. When an appropriate buoyancy is applied to the substrate, asshown in the third drawing of FIG. 25, the substrate S is maintained ina flat state.

The magnetic field forming part 300 is transferred to the upper side ofthe substrate S in a state in which buoyancy is applied to the substrateS, and then moves horizontally along the substrate S. At this time,power of the power supply 171 is applied to the assembly electrode 161 cvia the electrode connection part 213. That is, self-assembly proceedsin a state in which buoyancy is applied to the assembly surface of thesubstrate S.

According to the above description, it is not necessary to disposeseparate structures at the upper and lower sides of the substrate, andthe warpage phenomenon of the substrate can be corrected. Accordingly,even when an area of the assembly substrate is increased, the presentdisclosure enables to achieve a high self-assembly yield.

Meanwhile, the present disclosure allows self-assembly that can beperformed in a state in which the assembly substrate is almost flat. Inaddition, the present disclosure minimizes factors that interfere withthe self-assembly through control of movement of the substrate chuck,and prevents or avoids the semiconductor light-emitting diode from beingseparated from the assembly substrate after the self-assembly iscompleted.

For this, the controller 172 described in FIG. 7 controls the movementof the substrate chuck. Specifically, the controller 172 is configuredto control the movement of vertical and horizontal moving parts and arotating part provided at the substrate chuck 200. Meanwhile, thevertical moving part can be performed not only to move vertically theentire substrate chuck, but also to move vertically at least one of thefirst and second frames 210 and 220 and the fixing part 230 relative tothe other configuration. In the present specification, controlling thesubstrate chuck by the controller 172 such that the substrate movesvertically can include not only the meaning of vertically moving theentire substrate chuck, but also the meaning of vertically moving atleast one of the first and second frames 210 and 220 and the fixing part230 relative to the other configuration.

For example, controlling the substrate chuck by the controller 172 suchthat the substrate is lowered can include not only the meaning oflowering the entire substrate chuck, but also the meaning of lowering atleast one of the first and second frames 210 and 220 and the fixing part230. Since it can vary depending on a structure of the substrate chuck,the present disclosure is not limited thereto separately.

Hereinafter, a method of controlling the substrate chuck of thecontroller for applying buoyancy to the substrate described in FIG. 25will be described in detail.

The controller 172 controls a depth at which the substrate is submergedin the fluid based on a degree of warping of the substrate. For this,the present disclosure further includes a displacement sensor forsensing a degree of warping of the substrate. Specifically, thedisplacement sensor is configured to sense a distance between the sensorand a measurement target point. The displacement sensor can utilize aknown equipment or another equipment, and a detailed description thereofwill be omitted.

The displacement sensor 215 can be disposed at any one of the first andsecond frames 210 and 220 and the fixing part 230 provided in thesubstrate chuck, and can be configured to change the position thereof byseparate moving means. In the embodiment of FIG. 25, the displacementsensor 215 is shown as disposed on the second frame 220.

The displacement sensor senses a vertical distance between one point ofthe substrate and the displacement sensor on an upper side of thesubstrate. Specifically, the displacement sensor moves onto one point ofthe substrate, and then senses a distance between the displacementsensor and the substrate. Thereafter, the displacement sensor moves ontoanother point of the substrate, and then measures a distance between theanother point and the displacement sensor. At this time, thedisplacement sensor should move horizontally with respect to a referenceplane to sense the distance. Since the reference plane on which thedisplacement sensor moves is fixed, when a distance between each of aplurality of points on the substrate and the displacement sensor ismeasured, a degree of warping of the substrate can be known ordetermined.

For example, the displacement sensor disposed on the upper side of thesubstrate measures a distance from each of an edge and a central portionof the substrate. When the substrate is warped in a direction ofgravity, a vertical distance between one point of the edge of thesubstrate and the displacement sensor is smaller than that between onepoint of the central portion of the substrate and the displacementsensor.

Meanwhile, a reference height can be set by a user, and the distancemeasured by the displacement sensor can be converted based on areference value. For example, the reference value can be defined as adistance between an edge of the assembly surface and the displacementsensor. A measurement point for calculating the reference value can beset by the user.

When the distance value measured from the displacement sensor isconverted using the reference value, it can be used as a scale(hereinafter, referred to as a warpage value) indicating a degree ofabsolute warpage of the substrate. The warpage value can be calculatedas shown in Equation 1 below.

Warpage value=reference value−distance value measured by displacementsensor.  [Equation 1]

According to above Equation 1, when the warpage value has a positivevalue, it can be seen that the substrate is warped in a directionopposite to gravity. In addition, when the warpage value has a negativevalue, it can be seen that the substrate is warped in the gravitydirection. The controller 172 can determine whether the substrate israised or lowered according to signs of the warpage value.

In one embodiment, the displacement sensor senses a distance betweeneach of several points, such as 25 points (e.g., warpage values) of thesubstrate and the displacement sensor. Thereafter, the controller 172can convert the sensed values into a warpage value and control avertical movement distance and a vertical movement direction of thesubstrate based on maximum and minimum values among the 25 warpagevalues. Specifically, when an absolute value of the maximum value amongthe 25 warpage values is greater than that of the minimum value, thecontroller 172 determines that the substrate is entirely warped in theopposite direction to gravity, and controls the substrate chuck suchthat the substrate is raised. On the other hand, when an absolute valueof the minimum value among the 25 warpage values is greater than that ofthe maximum value, the controller 172 determines that the substrate isentirely warped in the gravity direction, and controls the substratechuck such that the substrate is lowered.

Since an increase in a depth at which the substrate is submerged in thefluid increases buoyancy acting on the substrate, the controller 172 canincrease the vertical movement distance of the substrate as the warpagevalue of the substrate increases. In one embodiment, when an absolutevalue of the maximum value among the 25 warpage values is greater thanthat of the minimum value, the controller 172 determines a risingdistance of the substrate in proportion to the absolute value of themaximum value. On the other hand, when an absolute value of the minimumvalue among the 25 warpage values is greater than that of the maximumvalue, the controller 172 determines a lowering distance of thesubstrate in proportion to the absolute value of the minimum value.

After the substrate is submerged in the fluid at a predetermined depth,the controller 172 can re-measure a degree of warping of the substrateusing the displacement sensor. Thereafter, the controller 172 determineswhether to raise or additionally lower the substrate according to are-measurement result. In one embodiment, the controller 172 can repeatthe above-described process until at least one of the maximum value andthe minimum value of the warpage value is within a predetermined value.

In another embodiment, the controller 172 can determine a depth at whichthe substrate is submerged in the fluid based on experimental data withrespect to the substrate. Specifically, before the substrate issubmerged in the fluid, a degree of warping of the substrate is sensedby the displacement sensor while the substrate is lowered at apredetermined distance. Even after the substrate is submerged in thefluid, the degree of warping of the substrate is sensed by thedisplacement sensor while the substrate is lowered at a predetermineddistance. When such sensing is repeated, it is possible to calculate acorrelation between a submerged depth of the substrate and an amount ofchange in the warpage of the substrate. Such an experiment can beperformed for each type of substrate.

When a specific type of substrate is used for self-assembly, thecontroller 172 senses a degree of warping of the specific type ofsubstrate, and then calculate the depth at which the substrate issubmerged in the fluid based on the sensing result and experimental dataon the specific type of substrate. Thereafter, the controller 172controls the substrate chuck such that the substrate is submerged in thefluid by the calculated depth. According to the above-described method,since it is not necessary to repeatedly sense the degree of warping ofthe substrate, the process time can be shortened.

Meanwhile, a correction result of the warpage of the substrate can beused for correcting the warpage of another substrate. Specifically,referring to FIG. 26, in the present disclosure, after the substrate issubmerged at a predetermined depth according to the above-describedexperimental data, a degree of warping of the substrate is re-measured.

At this time, in the present disclosure, a user selects whether tomeasure the degree of warping of the entire substrate or only a part ofthe substrate via the input part provided separately in the controller172 (S201—“Mode selection”).

Thereafter, a target position serving as a displacement measurementtarget and a reference position (reference value calculation targetposition) serving as a reference for a degree of warping of thesubstrate are input respectively (S202 to S204) (S202—“Initial referenceposition x,y value input”, S203—“Target input”, S204—“Reference positioninput”).

Thereafter, the controller 172 moves the displacement sensor to apredetermined measurement position (S205—“Move to #1 measurementposition”). The displacement sensor senses a distance between thedisplacement sensor and the substrate (S206—“Sensor Measurement”).Thereafter, the controller 172 moves the displacement sensor to a nextmeasurement position (S207—“Move to next position”). Whenevermeasurement of the displacement sensor is completed, the controller 172determines whether sensing of all target positions designated by theuser is completed (S208—“Comparison position measurement=All?”), andwhen the sensing is not completed (No of S208), the controller 172transfers the displacement sensor to a next measurement position (backto S207).

When sensing of all target positions is completed (Yes of S208), thecontroller 172 converts the sensing value into a warpage value, anddetermines whether at least one of the maximum value and the minimumvalue of the warpage values is within a predetermined range(S209—“Determination”).

When the warpage values are within the predetermined range (Yes ofS209), the controller 172 displays a measurement result on an outputpart provided separately (S211—“Measurement value display”), and updatesthe experimental data controlling the substrate chuck at the time ofcorrecting the warpage of the corresponding substrate (S212—“Reflectother unit offset value”), and uses at the time of correcting thewarpage of another substrate.

On the other hand, when the difference value is out of the predeterminedrange (No of S209), the controller 172 raises or lowers the substrate(S210—“Move by correction value”) according to a sensing result, andthen repeats operation S205.

Meanwhile, the controller 172 can control the substrate chuck such thata step in which the substrate is in contacted with the fluid and a stepin which the substrate is submerged in the fluid are performed stepwiseor sequentially. Bubbles can remain on a surface of the substrate in aprocess in which the substrate is in contact with the fluid. Thecontroller 172 performs control to minimize the bubbles until thesubstrate is in contact with the fluid, and performs control forapplying buoyancy to the substrate after the substrate is completely incontact with the fluid.

Specifically, after the controller 172 lowers the substrate chuck suchthat the assembly surface of the substrate is in contact with the fluid,the controller 172 can further lower the substrate chuck in a state inwhich the assembly surface of the substrate is in contact with thefluid.

The controller 172 can differentiate a speed of lowering the substrateuntil the entire assembly surface of the substrate is in contact withthe fluid and a speed of lowering the substrate when the substrate isfurther lowered.

In one embodiment, the controller 172 controls a substrate chuck suchthat a speed of lowering the substrate until the entire assembly surfaceof the substrate is in contact with the fluid is less than that oflowering the substrate chuck when the substrate is further lowered.Accordingly, the controller 172 ensures sufficient time for bubbles toescape to an edge of the substrate in a process of the substrate incontact with the fluid.

Further, in the present disclosure, in order to minimize bubbles formedbetween the substrate and the fluid, the substrate is contactedobliquely with the fluid when the substrate is in contact with thefluid. For this, the controller 172 controls a vertical moving part anda rotating part provided at the substrate chuck in the process of thesubstrate in contact with the fluid.

Specifically, the controller 172 controls the vertical moving part tolower the substrate until one end of the assembly surface is in contactwith the fluid in a state in which the assembly surface of the substrateis disposed obliquely with the surface of the fluid, and controls therotating part such that the assembly surface is in contact with thefluid along one direction, sequentially after one end of the assemblysurface is in contact with the fluid. Accordingly, the assembly surfaceof the substrate is in contact obliquely with the fluid. In thisprocess, the bubbles formed between the substrate and the fluid arepushed out of the edge of the substrate and finally pushed out of thesubstrate. Accordingly, the present disclosure minimizes the bubblesformed between the substrate and the fluid.

Thereafter, the controller 172 controls the vertical moving part tofurther lower the substrate.

As described above, the controller 172 minimizes bubbles formed betweenthe substrate and the fluid by bringing the substrate into contact withthe fluid obliquely in a process of lowering the substrate into thefluid.

Meanwhile, the controller 172 controls movement of the substrate chuckto prevent semiconductor light-emitting diodes from being separated fromthe substrate after self-assembly is completed. Specifically, after theself-assembly is completed, the substrate should be separated from thefluid, which can cause a problem that the semiconductor light-emittingdiode is separated from the substrate due to surface energy between thefluid and the semiconductor light-emitting diodes in a process ofseparating the substrate from the fluid.

In order to prevent such a problem, the controller 172 raises thesubstrate chuck submerged in fluid to a predetermined height after theself-assembly is completed, and then the controller 172 can furtherraise the substrate chuck such that the assembly surface of thesubstrate is separated from the fluid. Here, it is preferable that thepredetermined height is up to a surface height of the fluid.

The controller 172 can differently control a speed of raising thesubstrate to the predetermined height and a speed of further raising thesubstrate. In one embodiment, the controller 172 raises the substrate upto the surface height of the fluid at a high speed, and then separatesthe substrate from the fluid at a relatively slow speed. Accordingly,the present disclosure prevents the previously assembled semiconductorlight-emitting diode from being separated from the substrate in theprocess of separating the substrate from the fluid.

In addition, the controller 172 raises the substrate up to apredetermined height, and then drives the vertical moving part and therotating part such that the assembly surface of the substrate isseparated obliquely from the fluid. Specifically, the controller 172raises the substrate up to a predetermined height, and then controls therotating part such that the assembly surface is separated sequentiallyfrom the fluid along one direction.

At this time, the controller 172 can control a rotation speed of therotating part to change depending on a time. Specifically, thecontroller 172 can increase the rotation speed of the rotating part astime passes so that the substrate is quickly separated from the fluid.

As described above, the present disclosure prevents the previouslyassembled semiconductor light-emitting diode from being separated fromthe substrate in the process of separating the substrate from the fluidafter the self-assembly is completed.

The above-described disclosure is not limited to the configuration andmethod of embodiments described above, and the above embodiments can beconfigured by selectively combining all or part of each of embodimentssuch that various modifications can be performed.

What is claimed is:
 1. A device for self-assembling semiconductorlight-emitting diodes, the device comprising: an assembly chamber havinga space for accommodating a fluid; a magnetic field forming part havingat least one magnet for applying a magnetic force to the semiconductorlight-emitting diodes dispersed in the fluid and a moving part forchanging positions of the at least one magnet so that the semiconductorlight-emitting diodes move in the fluid; a substrate chuck having asubstrate support part configured to support a substrate, and a verticalmoving part for lowering the substrate so that one surface of thesubstrate is in contact with the fluid in a state in which the substrateis supported by the substrate support part; and a controller forcontrolling a movement of the magnetic field forming part and thesubstrate chuck, wherein the controller controls a depth at which thesubstrate is submerged in the fluid based on a degree of warping of thesubstrate.
 2. The device for self-assembling semiconductorlight-emitting diodes of claim 1, wherein the moving part is ahorizontal moving part to change the positions of the at least onemagnet along a horizontal direction of the assembly chamber.
 3. Thedevice for self-assembling semiconductor light-emitting diodes of claim1, wherein the substrate includes an assembly electrode, and wherein thesubstrate chuck further includes an electrode connection part forapplying power to the assembly electrode to generate an electric fieldso that the semiconductor light-emitting diodes are placed atpredetermined positions of the substrate in a process of moving thesemiconductor light-emitting diodes by a position change of the at leastone magnet.
 4. The device for self-assembling semiconductorlight-emitting diodes of claim 1, further comprising: a displacementsensor for sensing the degree of warping of the substrate. wherein thecontroller controls the depth at which the substrate is submerged in thefluid based on the sensed degree of warping of the substrate by thedisplacement sensor.
 5. The device for self-assembling semiconductorlight-emitting diodes of claim 1, wherein the controller lowers thesubstrate such that an assembly surface of the substrate is in contactwith the fluid, and then further lowers the substrate in a state inwhich the assembly surface of the substrate is in contact with the fluid6. The device for self-assembling semiconductor light-emitting diodes ofclaim 5, wherein the substrate chuck includes a rotating part forrotating the substrate support part, and wherein the controller furtherdrives the vertical moving part and the rotating part such that theassembly surface of the substrate is obliquely in contact with the fluidwhen lowering the substrate such that the assembly surface of thesubstrate is in contact with the fluid.
 7. The device forself-assembling semiconductor light-emitting diodes of claim 6, whereinthe controller: controls the vertical moving part to lower the substrateuntil one end of the assembly surface is in contact with the fluid in astate in which the assembly surface of the substrate is obliquelydisposed to a surface of the fluid, and controls the rotating part suchthat areas of the assembly surface sequentially comes in contact withthe fluid along one direction after one end of the assembly surfacecomes in to initial contact with the fluid.
 8. The device forself-assembling semiconductor light-emitting diodes of claim 7, whereinthe controller controls the vertical moving part to further lower thesubstrate into the fluid after the entire assembly surface comes incontact with the fluid.
 9. The device for self-assembling semiconductorlight-emitting diodes of claim 6, wherein after the semiconductorlight-emitting diodes are placed at predetermined positions of thesubstrate, the controller further raises the substrate such that theassembly surface of the substrate is separated from the fluid after thesubstrate is raised up to a predetermined height.
 10. The device forself-assembling semiconductor light-emitting diodes of claim 9, whereinin raising the substrate up to the predetermined height, the controllerdrives the vertical moving part and the rotating part such that theassembly surface of the substrate is obliquely separated from the fluid.11. The device for self-assembling semiconductor light-emitting diodesof claim 10, wherein in raising the substrate up to the predeterminedheight, the controller controls the rotating part such that the assemblysurface is sequentially separated from the fluid along one direction.12. The device for self-assembling semiconductor light-emitting diodesof claim 11, wherein the controller controls a change in a rotationspeed of the rotating part so that the assembly surface is sequentiallyseparated from the fluid along one direction.
 13. The device forself-assembling semiconductor light-emitting diodes of claim 1, whereina force of buoyancy applied to the substrate by the fluid increases withan increase in the depth at which the substrate is submerged in thefluid.
 14. The device for self-assembling semiconductor light-emittingdiodes of claim 1, wherein the degree of warping of the substrate isbased on a weight of the substrate.
 15. A device for self-assemblingsemiconductor light-emitting diodes to a substrate, the devicecomprising: an assembly chamber having a space for accommodating afluid; at least one magnet configured to apply a magnetic force to thesemiconductor light-emitting diodes dispersed in the fluid; a substratesupport configured to support the substrate having an assemblyelectrode; a vertical mover configured to lower the substrate support sothat one surface of the substrate is in contact with the fluid in astate in which the substrate is supported by the substrate support; anda controller configured to control a movement of the at least one magnetand the substrate support, wherein the controller controls a depth atwhich the substrate is submerged in the fluid.
 16. The device forself-assembling semiconductor light-emitting diodes to a substrate ofclaim 15, wherein the depth is determined based on a degree of warpingof the substrate caused by a weight of the substrate.
 17. The device forself-assembling semiconductor light-emitting diodes to a substrate ofclaim 15, further comprising a horizontal mover for changing positionsof the at least one magnet so that the semiconductor light-emittingdiodes move in the fluid.
 18. The device for self-assemblingsemiconductor light-emitting diodes to a substrate of claim 15, whereina force of buoyancy applied to the substrate by the fluid increases withan increase in the depth at which the substrate is submerged in thefluid.
 19. The device for self-assembling semiconductor light-emittingdiodes to a substrate of claim 15, wherein the substrate includes anassembly electrode, and wherein the device further includes an electrodeconnection part for applying power to the assembly electrode to generatean electric field so that the semiconductor light-emitting diodes areplaced at predetermined positions of the substrate in a process ofmoving the semiconductor light-emitting diodes by a position change ofthe at least one magnet.
 20. The device for self-assemblingsemiconductor light-emitting diodes to a substrate of claim 15, furthercomprising: a displacement sensor configured to sense the degree ofwarping of the substrate. wherein the controller controls the depth atwhich the substrate is submerged in the fluid based on the sensed degreeof warping of the substrate by the displacement sensor.